Add basic etcd registry implementation

registry/etcd/watcher.go

@@ -0,0 +1,73 @@
+package etcd
+
+import (
+	"github.com/coreos/go-etcd/etcd"
+	"github.com/myodc/go-micro/registry"
+)
+
+type etcdWatcher struct {
+	registry *etcdRegistry
+	stop     chan bool
+}
+
+func newEtcdWatcher(r *etcdRegistry) *etcdWatcher {
+	ew := &etcdWatcher{
+		registry: r,
+		stop:     make(chan bool),
+	}
+
+	ch := make(chan *etcd.Response)
+
+	go r.client.Watch(prefix, 0, true, ch, ew.stop)
+
+	go func() {
+		for rsp := range ch {
+			if rsp.Node.Dir {
+				continue
+			}
+
+			s := decode(rsp.Node.Value)
+			if s == nil {
+				continue
+			}
+
+			r.Lock()
+
+			service, ok := r.services[s.Name]
+			if !ok {
+				if rsp.Action == "create" {
+					r.services[s.Name] = s
+				}
+				r.Unlock()
+				continue
+			}
+
+			switch rsp.Action {
+			case "delete":
+				var nodes []*registry.Node
+				for _, node := range service.Nodes {
+					var seen bool
+					for _, n := range s.Nodes {
+						if node.Id == n.Id {
+							seen = true
+							break
+						}
+					}
+					if !seen {
+						nodes = append(nodes, node)
+					}
+				}
+				service.Nodes = nodes
+			case "create":
+				service.Nodes = append(service.Nodes, s.Nodes...)
+			}
+			r.Unlock()
+		}
+	}()
+
+	return ew
+}
+
+func (ew *etcdWatcher) Stop() {
+	ew.stop <- true
+}